Corrugation apparatus

ABSTRACT

An apparatus for the continuous polygonal corrugation of hot sheets of thermoplastic material has continuous elements formed of metallic wires welded end-to-end. These elements are arranged in space at the locations where the sheets should normally be bent for producing the desired corrugation. The elements moving with the sheets during passage thereof through the apparatus.

V 0 United States Patent 1 1 3,744,952 Bequet et al. 1 July 10, 1973CORRUGATION APPARATUS [56] References Cited [75] Inventors: JeanFrancois Bequet, Brussels; UNITED STATES PATENTS Roger Van Asbmck,Neerijse; Paul 2,513,777 7/1950 Andre 156/205 x Du Bois, Braine-LAlleud,all Of 2,695,652 11/1954 Segil 18/19 A Belgium 3,102,776 9/1963Steinmann et a1. 18/19 A X 2,l58,087 5 1939 R 264 287 {73] Assignee:Solvay & Cie, Brussels, Belgium I owe c I [22] Filed: Dec. 30, 1970Primary ExaminerH. A. Kilby, Jr. pp No.2 102,606 Attorney-Spencer & KayeH D 57 ABSTRACT [30] Forms App canon Prmnty am An apparatus for thecontinuous polygonal corrugation Dec. 31, 1969 Belgium 83422 of hotsheets of thermoplastic material has continuous elements formed ofmetallic wires welded end-to-end. [52] US. Cl. 425/336, 425/396 Theseelements are arranged in space at the locations E 3 1 where the sheetsshould normally be bent for producing the desired corrugation. Theelements moving with the sheets during passage thereof through theapparatus.

7 Claims, 4 Drawing Figures 6 511 l l l l T R .l .l. d

Patented July '10, 1973 3,744,952

2 Sheets-Sheet l Fig.1

I i 1 r"r\(1 T TT'FT' 12 n ,5 6 11 INVENTORS. Jean Francois Bequet RogerVon Asbroeck Poul Dubois Pate :nted Jul 10, 1973 2 Sheets-Sheet 2INVENTORS.

Jean Francois Bequei Roger Van Asbroec-k Paui Dubois ATTOREYS.

CORRUGATION APPARATUS CROSS-REFERENCE TO RELATED APPLICATION Thisapplication is related to applicants copending application Ser. No.102,607 filed on Dec. 30, 1970 now Pat. No. 3,661,694 based on BelgianPat. No. 743,922 which issued on an Application filed in Belgium on Dec.31, 1969.

BACKGROUND OF THE lNVENTlON The present invention concerns a device forthe continuous polygonal corrugation of hot sheets constructed of athermoplastic material. This device is of particular advantage when thesheets intended to be corrugated have previously been subjected to abidirectional orientation.

Among the various configurations of corrugated sheets of thermoplasticmaterial which are on the market at present, those having a polygonalcross section are very successful.

Up to now, these sheets have been made by, for example, using deviceswhich grip the edges of the sheets to be treated and, while the latterare being softened as a result of a previous heat treatment, the sheetsare then passed through a corrugating device which comprises a fixedmold and a counter-mold. The terminal portion of these molds has coolingsystems, such as circulating cold fluids, which solidify the sheet inthe form determined by the geometry of the forming molds.

This corrugating operation is accompanied by a slight stretching, bothin the transverse and longitudinal directions. However, thebidimensional orientation given to the corrugated sheet remains verylow.

If it is desired to produce corrugated sheets with such devices byutilizing sheets of thermoplastic material having previously beensubjected to an advantageous bidimensional orientation treatment, itshould first be noted that the forces of friction against the fixedmolds are such that the sheets are susceptible to being torn.

It is particularly desirable to be able to produce corrugated sheetsstarting from flat sheets of thermoplastic material which have beensubjected to such previous biorientation treatment, since the lattergives to the finished products improved mechanical properties such asincreased impact resistance.

lf materials such as rigid vinyl chloride are used, the increase of theimpact resistance eliminates the necessity of adding reinforcing agents,which are always costly and often are of a very restricted and/ortemporary effectiveness.

in order to reduce the forces of friction between the sheet and theshaping molds during, for example, the corrugation of the biorientedsheets of thermoplastic material, the possibility has been considered ofutilizing another device known per se in which the forming members movewith the sheets during the shaping operation.

Such a device comprises two corrugating trays between which passes thesheet of softened thermoplastic material to be corrugated. These trayssupport movable chains which are disposed at regular intervals and aredriven by driving sprockets mounted on an axis behind the corrugatingtrays. On these endless chains are fixedly mounted a plurality ofshaping shells which are consecutive and contiguous and which produce acontinuous profile when in contact with the sheet of thermoplasticmaterial to be treated. The shells have a shape such that by bringingthe two trays together, the shells become interdigitated to produce thecorrugating profile desired.

The applicants have, however, observed that this type of apparatus wouldnot permit the production of regularly arranged, corrugated articles,and that it would mean a substantial expense of calories.

For example, corrugation tests have shown that in spite of the care withwhich the shells are made, there are irregularities in the corrugatedarticles at the junction between nearly all the sheets. Theseirregularities are the result of:

1. small differences in the geometry of the shells and the links of thechains;

2. slight play which exists during the mounting of the shells on thechains, with the result that the shells are laterally off-set orslightly pivoted; and

3. stresses applied to the shells with the result that,

consecutive shells are disconnected during operation.

The first two causes of irregularities can be decreased by calibratingeach shell and by bringing modifications to the system of mounting theshells on the chains. The third cause can be minimized by reinforcingthe chains in order to reduce their elongation under the effect of thetensions applied during the operation.

These improvements are, however, very costly, because a large number ofshaping shells is required and the process is relatively inefficient.

On the other hand, in the case sheets made of a rigid vinyl chlorideresin especially polyvinyl chloride the sheets which are subjected tocorrugation should be heated to a temperature of l20 C when they arebidirectionally oriented and from 90-l 35 C if there is no suchtreatment.

However, when the corrugation of these sheets is carried out they shouldbe cooled down, while retaining their shape, to a temperature which islower than the glass transition temperature of the resin so that thecorrugated articles will keep their shape at room temperature.

It is, therefore, desirable to adjust the temperature of the shapingshells to the thermic cycle of the thermoplastic material which is usedby, for example, preheating the shells before they contact the sheets tobe treated and by cooling them after they contact the sheets.

independently of the fact that this thermic cycle to which the shellshave been submitted is a fourth irreducible cause of formation ofirregularities on the corrugated articles, it should be noted that thesesuccessive operations of reheating and cooling constitute a costlyexpense of energy which, depending on the shapes and the weights of theshells, uses up to 3 to 10 times more calories than the heating of thesheet to its corrugating temperature.

SUMMARY OF THE INVENTION An object of the present invention is toprovide a corrugating device which enable the aforementioneddisadvantages to be economically overcome.

The corrugating device according to the present invention is providedwith endless elements formed of metallic wires which are weldedend-to-end and are mounted and held in space exactly where the sheetsshould be bent to produce the corrugation desired; the

endless elements accompanying the sheets during their passage throughthe device.

During the progressive corrugation of the sheets, these endless elementsare held from behind that is, from the side thereof which is not incontact with the sheets either by fixed supports which areselflubricating and anti-wear or by movable supports which are displacedat a speed which is substantially equal to that of the treated sheets.

Means for heating the endless elements may be provided ahead of thelocation where they come into contact with the sheets to be corrugated,and means to cool down these endless elements should be disposedsubsequent to this same location.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side elevationview of a device according to the invention.

FIG. 2 is a schematic end view of a portion of the device of FIG. 1illustrating the position of the continuous element when a corrugatedarticle of trapezoidal form is made.

FIG. 3 is a perspective view, partly in cross section, illustrating theshells which support the continuous elements;

FIG. 4 is an end view of a portion of a shell according to FIG. 3 alongwith an endless element shown in crosssection.

DESCRIPTION OF TI-IE PREFERRED EMBODIMENTS As illustrated in thedrawings, the corrugating device has a conventional frame, notillustrated, on which are mounted in a known manner two corrugatingtrays 1 and 2. Trays 1 and 2 are mounted for movement toward and awayfrom one another and can be arranged close to or distant from oneanother.

Each corrugating tray 1,2 is provided with suitable known endless chain3. Chain 3 are uniformly spaced and judiciously disposed depending onthe corrugating profile which is desired. These endless chains 3 aredriven by means of suitable known driving sprockets 4 and move onrespective guide rails 5. The endless chains 3 support a series ofcorrugating fingers formed by U-shaped shells 6 the upper edges of eachleg of which define notches 7 dimensioned to receive and hold endlesselements 8 which are, for example, formed of metallic wires weldedend-to-end. The wires forming elements 8 may be made for example, of asuitable steel.

The geometric form and the arrangement of the series of shells 6 aresuch that when the corrugating trays l and 2 are brought close togetherthe shells 6 of the trays 1,2 are interdigitated in dependence on thecorrugated cross section 9 desired, as shown in FIG. 2.

As illustrated in FIG. 1, thereturn path 10 of the elements 8 canadvantageously be different from that of the shells 6 in order toprevent the radiuses of curvature of elements 8 from producing stresseswhich are higher than the limit of elasticity of the material whichconstitutes the elements 8. That is, the radiuses of curvature aredimensioned to maintain the stresses in elements 8 below the limitedelasticity of their material. In this case, it would appear useful toprovide guiding ele- 5 ments 1] at the end of and even at the beginningof the 6 return paths of elements 8 in order to make sure that thevarious elements 8 are directly arranged and held in the notches 7 ofthe shells 6. The rigidity of the elements 8 themselves will cause themto follow path 10.

The travelling speed of the shells 6 should be substan tially equal tothe speed of the sheet to be treated. In this manner, when thecorrugating trays I, 2 are brought close together, the elements 8 areheld between the shells 6 and a sheet to be corrugated (not shown) andare driven at the same speed as the latter.

The device may also have conventional heating elements 12 for heatingthe elements 8. These elements 12 which may be, for example, electricresistance heaters, are mounted ahead of the adjacent elements 8upstream of the point where the elements 8 come into contact with thesheet of thermoplastic material to be corrugated. The device can alsohave conventional cooling elements 14 for cooling the elements 8.Elements 14 may be, for example, cold air jets 14 which are directedtowards the sheet and the elements 8 downstream of the point where thissheet is completely brought into its desired corrugated form. Theelements 8 should, for example, be heated to a temperature in the rangeof to C for bidirectionally oriented sheets and 90 to l35 C foruntreated sheets, and cooled to a temperature below the glass transitiontemperature of the resins. With the apparatus described above, theapplicants have produced corrugated sheets in accordance with thecross-sectional profile of FIG. 2 from sheets made of rigid,bidirectionally oriented vinyl chloride resins. The following advantages have been found:

1. the edges of the corrugated articles are well defined and areregular. The aspect of the corrugated sheets is not deformed by shells 6which are irregular or are badly disposed on the endless chains 3,because the elements 8, which extend out from these shells 6, are rigidenough to perfectly realign the shells 6. In addition, elements 8 havecontinuous profiles which are firmly and substantially in contact withthe sheets during the corrugation. As illustrated in FIG. 3, theconsecutive shells 6 are not necessarily contiguous, as long as thedistance which separates two consecutive shells 6 is not such that theelements 8 sag under the action of the sheet of thermoplastic materialto be corrugated;

the cost of the apparatus is substantially lower since it is notnecessary to use shells 6 which have been precision machined, norendless chains 3 that will not lose their shape; and

3. the output in calories is substantially decreased since it issufficient that only the elements 8 be thermically conditioned.Furthermore, the calorie losses by conductivity between the elements 8and the shells 6 can easily be reduced to a minimum by making thenotches'7 in such a manner that the latter are in contact with theelements 8 only along two generating lines of these elements 8, thelatter being preferably of a circular cross section. That is, as can beseen from FIG. 4, an element 8 with circular cross section contacts anotch 7 only at two points of the surface of the elements 8. Elements 8are shown in phantom lines in FIG. 3 to clearly show notches 7. Thecalorie losses may also be reduced by forming cut-out portions 13 (FIG.3) in the walls of the shells 6.

Even though the device according to the present invention would appearto be particularly useful for producing a polygonal corrugation ofbidirectionally oriented sheets of plastic material, it may also be usedwith advantage to produce corrugated articles from sheets ofthermoplastic material which have not previously been bioriented.Examples of bidirectionally oriented sheets suitable for use with thepresent apparatus may be found in applicants copending applicationreferred to on Page 2 of this specification.

it is, however, to be understood that the embodiment described above isnot intended to limit the scope of the present invention, since it isobvious that the device which is described can be modified withoutdeparting from the scope or spirit of the invention. in particular, thesupports for the continuous elements 8 have been indicated as movable,but it is apparent that these supports may also be fixed in place bysuitable, known selflubricating and anti-wear devices.

it will be understood that the above description of the presentinvention is also susceptible to various other modifications, changesand adaptations, and the same are intended to be comprehended within themeaning and range of equivalents of the appended claims.

W e claim:

1. in apparatus for the continuous longitudinal corrugation of hotsheets of thermoplastic material having a predetermined speed anddirection of movement along a flow path through the apparatus, theimprovement comprising, in combination:

a. first and second tray means arranged opposite one another and havingcorrugating fingers arranged in an interdigitating manner for defining apredetermined longitudinal corrugation in a sheet moving longitudinallyalong the flow path through the apparatus; and means associated witheach of said tray means and arranged for movement in the direction ofmovement of the sheets of thermoplastic material at a speedsubstantially the same as the speed of the sheets of material and beinga plurality of endless elements formed of metallic wires fastenedtogether end-to-end.

2. An apparatus as defined in claim 1, wherein each of said tray meansis mounted for selective movement toward and away from the other of saidtray means.

3. in apparatus for the continuous corrugation of hot sheets ofthermoplastic material having a predetermined speed and direction ofmovement along a flow path through the apparatus, the improvementcomprising, in combination:

a. first and second tray means arranged opposite one another and mountedfor selective movement toward and away from each other, each tray meanshaving corrugating fingers formed by a plurality of U-shaped shells andarranged in an interdigitating manner for defining a predeterminedcorrugation in a sheet moving along the flow path through the apparatus;

. means associated with each of said tray means and arranged formovement in the direction of movement of the sheets of thermoplasticmaterial at a speed substantially the same as the speed of the sheets ofmaterial and being a plurality of endless elements formed of metallicwires fastened together end-to-end; and

. movable endless chains, with said U-shaped shells mounted on saidendless chains and each having a pair of legs each of which defines anotch dimensioned to receive and hold a respective one of said endlesselements and arranged to put said endless elements in contact with thesheets of thermoplastic material.

4. An apparatus as defined in claim 3, wherein said endless elements andsaid shells have return paths and the return paths of said endlesselements are different from the return paths of said shells and haveradiuses of curvature dimensioned to maintain the stresses in saidendless elements below the limit of elasticity of the metallic materialfrom which said endless elements are made.

5. An apparatus as defined in claim 4, further including means arrangedadjacent the beginning and the end of the return path of each of saidendless elements for guiding said endless elements and for directlyarranging said endless elements in said notches.

6. An apparatus as defined in claim 5, further including means arrangedadjacent the end of the return path of each of said endless elements forheating said endless elements.

7. An apparatus as defined in claim 6, further including means forcooling the corrugated sheet and said endless elements and arrangedafter the point where the sheet of thermoplastic material is completelybrought to the corrugated desired form.

1. In apparatus for the continuous longitudinal corrugation of hotsheets of thermoplastic material having a predetermined speed anddirection of movement along a flow path through the apparatus, theimprovement comprising, in combination: a. first and second tray meansarranged opposite one another and having corrugating fingers arranged inan interdigitating manner for defining a predetermined longitudinalcorrugation in a sheet moving longitudinally along the flow path throughthe apparatus; and b. means associated with each of said tray means andarranged for movement in the direction of movement of the sheets ofthermoplastic material at a speed substantially the same as the speed ofthe sheets of Material and being a plurality of endless elements formedof metallic wires fastened together end-to-end.
 2. An apparatus asdefined in claim 1, wherein each of said tray means is mounted forselective movement toward and away from the other of said tray means. 3.In apparatus for the continuous corrugation of hot sheets ofthermoplastic material having a predetermined speed and direction ofmovement along a flow path through the apparatus, the improvementcomprising, in combination: a. first and second tray means arrangedopposite one another and mounted for selective movement toward and awayfrom each other, each tray means having corrugating fingers formed by aplurality of U-shaped shells and arranged in an interdigitating mannerfor defining a predetermined corrugation in a sheet moving along theflow path through the apparatus; b. means associated with each of saidtray means and arranged for movement in the direction of movement of thesheets of thermoplastic material at a speed substantially the same asthe speed of the sheets of material and being a plurality of endlesselements formed of metallic wires fastened together end-to-end; and c.movable endless chains, with said U-shaped shells mounted on saidendless chains and each having a pair of legs each of which defines anotch dimensioned to receive and hold a respective one of said endlesselements and arranged to put said endless elements in contact with thesheets of thermoplastic material.
 4. An apparatus as defined in claim 3,wherein said endless elements and said shells have return paths and thereturn paths of said endless elements are different from the returnpaths of said shells and have radiuses of curvature dimensioned tomaintain the stresses in said endless elements below the limit ofelasticity of the metallic material from which said endless elements aremade.
 5. An apparatus as defined in claim 4, further including meansarranged adjacent the beginning and the end of the return path of eachof said endless elements for guiding said endless elements and fordirectly arranging said endless elements in said notches.
 6. Anapparatus as defined in claim 5, further including means arrangedadjacent the end of the return path of each of said endless elements forheating said endless elements.
 7. An apparatus as defined in claim 6,further including means for cooling the corrugated sheet and saidendless elements and arranged after the point where the sheet ofthermoplastic material is completely brought to the corrugated desiredform.